1. Field of the Invention
The present invention relates to a trim and tilt apparatus for a marine vessel propulsion machine.
2. Description of the Background Art Japanese Patent No. 2963511 describes a trim and tilt apparatus for a marine vessel propulsion machine which allows the marine vessel propulsion machine to perform a trim operation and a tilt operation. Specifically, the trim and tilt apparatus for the marine vessel propulsion machine described in Japanese Patent No. 2963511 includes a large-diameter cylinder and a small-diameter cylinder formed in series and in communication with each other. During a trim-up operation, hydraulic oil discharged by a pump is supplied to the large-diameter cylinder to push a large-diameter trim piston in the large-diameter cylinder up toward the small-diameter cylinder. During a tilt-up operation, after the trim piston reaches a maximum trim-up position, the hydraulic oil discharged by the pump is further fed to the large-diameter cylinder. The hydraulic oil then flows through a through-path provided in the trim piston and is filled into the small-diameter cylinder located below a tilt piston. The hydraulic oil thus moves only the tilt piston to a maximum tilt-up position.
[Patent Literature 1] Japanese Patent No. 2963511
The trim and tilt apparatus for the marine vessel propulsion machine described in Japanese Patent No. 2963511 has the following problems.
(1) During the tilt-up operation, the hydraulic oil discharged by only one pump is supplied to the small-diameter cylinder. This increases time needed to fill the small-diameter cylinder with the hydraulic oil and thus increases a tilt operation duration until the maximum tilt-up.
(2) At the end of the tilt-up operation, the pressure of the hydraulic oil acting to push the trim piston up toward the small-diameter cylinder is not applied. Thus, to retain the trim piston at a stroke end in a trim-up direction after the tilt-up operation ends, trim piston push-up means such as spring force or gravity is needed which constantly pushes up the trim piston toward the small-diameter cylinder.
An object of the present invention is to provide a trim and tilt apparatus for a marine vessel propulsion machine which serves to reduce the tilt-up operation duration until the maximum tilt-up and which allows the piston to be retained at the maximum tilt-up position at the end of the tilt-up operation without using the piston push-up means.